1. Field of the Invention
The present invention relates to a fusing apparatus. More particularly, the present invention relates to a fusing apparatus including a fusing roller maximizing an induced heating efficiency of a heated substance by adhering a heating unit onto the heated substance using an elastic material to concentrate a magnetic flux on the heated substance.
2. Description of the Related Art
Generally, an image forming apparatus using an electrophotographic method, such as a laser printer or a digital copying machine, prints a mono-color image or a full-color image by forming an electrostatic latent image by scanning light onto a photosensitive medium charged to a predetermined electric potential. The electrostatic latent image is developed using toner of a predetermined color stored in a developing unit. The developed image is transferred and fused onto a sheet of paper.
The electrophotographic image forming apparatus may be classified into a wet type image forming apparatus and a dry type image forming apparatus.
The wet type electrophotographic image forming apparatus uses a developer, which is made by distributing powder toner in a liquid carrier. The dry type electrophotographic image forming apparatus uses a binary developer, in which powder carrier and toner are mixed, or a single developer without the carrier. Hereinafter, the dry type electrophotographic image forming apparatus will be described, and the developer will be referred to as toner.
FIG. 1 is a transversal cross-sectional view of a fusing apparatus using a halogen lamp as a heat source, according to the conventional art. FIG. 2 is a longitudinal cross-sectional view along line I-I′ of FIG. 1.
The fusing apparatus 10 includes two cylindrical fusing rollers 11 and 12 formed of aluminum, which contact each other in a lengthwise direction. Both ends of the fusing rollers 11 and 12 are supported by bearings 14. Coating layers 13 are formed on surfaces of the fusing rollers 11 and 12 to form a nip for heating and fusing an image onto a piece of paper passing between the rollers 11 and 12.
A heating unit 15 that uses a halogen lamp as a heat source is connected to an external power source (not shown) to generate heat. The heating unit 15 is installed in each fusing roller 11 or 12. The heating unit 15 is separated from the fusing roller 11 or 12, and air is filled therebetween.
When an electric current from the external power source (not shown) is applied to both ends of the heating unit 15, the heating unit 15 generates radiation energy that is transmitted to inner walls of the fusing rollers 11 and 12 through the air. A light/heat conversion layer formed as a black body converts the radiation energy into heat energy. The heat energy is transmitted to an image 21 on a recording medium 20 that passes through the fusing rollers 11 and 12 that contact each other. Therefore, the image 21 is melted by the heat energy, and fused on the recording medium 20.
However, the fusing apparatus using the halogen lamp as the heat source has the following problems.
When the power source is turned on to perform a printing operation, a long warm-up time is required until the temperature of a fusing roller reaches the fusing temperature from normal temperature. A user should wait until the fusing roller reaches the fusing temperature before performing the printing operation.
Additionally, since the halogen lamp and the fusing roller are separated from each other and air is filled therebetween, the heat generated by the halogen lamp heats the fusing rollers by radiation, and passes through the fusing rollers by conduction. Therefore, the heat transmission speed is low, and heat efficiency is reduced.
Accordingly, a need exists for a fusing roller of a fusing apparatus that reduces the warm-up time and improves heat efficiency.